Flow meter



FLOW M TER I Original Filed Aug. 15, 1934 4 Sheets-S heet 1 Feb. 21,1939. w. c. WALKER "Re. 21,012

" FLOW METER Original Filed Aug. 15, 1934. 4 Sheets-She'et 2 Feb. 21,1939. wcwALKs 21.012

FLOW METER Original Filed Aug. 15, 19:54 4 Sheets-Sheet 3 FIG. 7. s5

FIG- 8.

mmnsm w. c. W-ALKER 21,012

Fen-21, 1939.

FLOW METER gori inai Filed Aug. 15. 19:54 4 Sheets-Shut 4 FIG. 10'

III

- nw; 2.4a;

Reissued Feb. 21, 1939 This application relates to flow meters. More 1relates to that general type of flow meter which utilizes the pressuredifferential particularly, it

OFFICE FLOW METER William C(Walkcr, York, Pa.

Original No. 2,077,444, dated rial No. 739,985, August 15, for reissueAugust 21, 1937,

Aprll 20, 1937, Sc-

1934. Application Serial No. 160,295

14 claims, -(01. wa -zoo) occurring adjacent a restricted aperture in a5 conduit for the purpose ofactuating mechanism by which the volume-offluid passing through the conduit may be It is a genera vide a flowmeter registered. 1 object of this invention to proof this general typewhich may be simply and cheaply constructed, and yet registerexceptionally accurately the volume of fluid passing through theprincipal conduit.

Flow meters in general use at the present time most instances employ a.manometer which in fluctuates respo the primary conduit.

nsive to the changes in head in It is an object of this invention toproduce a satisfactory meter which will eliminate the use of a manometerand which will therefore permit a much greater range and eliminate theuse'of the...very heavy and often expensive manometric fluids requiredby the meters of the prior art.

In general, it is further the object of the invention to provide a. flowmeter in which the 5 pressure differential developed adjacent theorilice in the cond uit is used for passing a member having a. secondaryorifice through a relatively stationary body of liquid in order that bymeasurlng the movement of the member with respect to the body of liquidthrough which it moves,

the volume of flowthrough the primary conduit may be determined.

Although the invention herein illustrated is particularly adaptable foruse with primary con- -dults having a apparent that it restrictedorifice or throat it is may be used in connection with a Pitot tube orany other device where a pressure differential An object of paratus ofthis is set up by the flow the primary conduit.

01' fluid through the invention is to provide apgeneral type which willbe extremely rugged and easily adjusted, in order that it may be usedfor relatively permanent installations and will require a minimum ofcare.

Still further the invention contemplates provision of apparatus. of thisgeneral type which will be suiliciently accurate for mostpractical'installations and which will maintain high efficiencyregardless of fluctuations in volume of flow through the primaryconduit.

A consideration of the following specification in connection with theaccompanying drawings .will reveal man i advantages.

y other and further objects and of the arrows;

Fig. 6 is a sectional view showing the internal portions of thereversing valve;

Fig. 7 is a diagrammatic view of a modified form of the apparatusillustrating the manner in which the meter may be connected to theconduit with which it is to be used;

Fig. 8 is a side elevation of the diagrammatic view shown in Fig. 7, theelectrical connections having been omitted;

Fig. 9 illustrates a modified use of the drum for use in measuring theflow of liquids in which the drum is partially filled with a liquidlighter than the liquid being metered; and

Figs. 10, 11, and 12 are enlargedviews of various forms of orifices forcontrolling communication between the chambers of the drum.

With reference to the drawings, the apparatus includes a supportingbracket l, (Figs. 1 and 5) 3 adapted to be secured to a wall or othersimilar surface on which the meter may be mounted. The supportingbracket I has a forwardly extending web 2, which serves to rigidlysupport a shelf portion 3, extending outwardly from the upper end of thebracket l.

The web and shelf portions 2 and 3 respectively are recessed to form asemi-cylindrical walled well 4 in the shelf for the reception of themovable portion of the apparatus which will now be described. Mountedupon the upper surface of the shelf 3 are a pair of bearing supports 5adjacent the edgev of the well 4. Each serves to house an annular seriesof ball bearing members 6. A shaft 1 is mounted-for rotation in thebearing 6. This shaft 1 has an axial central portion of slightlyincreased diameter and contains a pair of axially disposed bores 8 and 9extending inwardlyfrom the ends of the shaft almost meeting each other.It is apparent from this construction that a wall Ill remains in thecentral portion of the shaft 1, preventing communication between thebores 8 and ll. One end of the shaft 1 is reduced in diameter to form acylindrically axially extending portion ll of sub- -of this drum isclearly seen A casting I2 is mounted adjacent the outer end of the shaft1 and has a bore I3 therein adapted to receive the end portion II of theshaft 1. The portion of the casting I2 into which the shaft 1 extends issubstantially cylindrical and threaded to receive a'packing nut I4serving to compress packing material l5 around the cylindrical portionII of the shaft 1. From the construction just described, it will beapparent that the axial bore 9 communicates with the bore l3 in thecasting by means of a fluid tight joint, which will permit thetransmission of fluid from the bore I3 into the bore 9 and which willalso permit a relatively'free rotation of the shaft 1 with respect tothe casting I2.

The opposite end of the shaft I is likewise formed with a reducedcylindrical portion I8 extending into a casting I9 provided with aninternal bore substantially the same in function and construction as thecasting I2 just described. Likewise, a fluid tight joint is maintainedbetween the axial bore 8 and the passage 20 by means of a packing glandnut 2| and packing 22. Thus, it will be seen that the shaft 1 may rotaterelatively freely within the bearing 6 while the internal bores 8 and 9are maintained in constant communication with the bores 20 and I3respectively in the castings I9 and I2.

A cylindrical drum 25, mounted for partial rotatlon, is secured on theshaft 1 in any suitable manner which will prevent relative movement ofthe drum and shaft; The internal construction trically mounted on saidshaft inside said drum is a cylindrical partition wall 26, supported bya plurality of radially extending webs 21, the partition wall 26 formingwith the drum an annular chamber 28 surrounding the shaft and spaced asubstantial radial distance therefrom.

The annular chamber stantially semi-circular compartments 23 and 29. bymeans of a pair of radially disposed webs 30 extending from the wall 26to the outer wall of the drum 25. The axial ends of this drum 25 areclosed by means of suitable fluid tight walls 3| and 32. Thus it will beseen that the interior of the drum contains two fluid tightsubstantially semi-annularlv extending chambers.

An orifice 33 is provided in the radially disposed web 30 to providemeans of communication between the chambers.

on the end wall 3| of the drum is mounted a housing 31 which encloses apair of conduits 35 and 38, each communicating with one of the chamberswithin the drum by means of suitable apertures in the wall 3|. Theopposite end of the conduit 35 communicates with the bore 8 in the shaftI and the conduit 36 communicates with the bore 9 in the shaft 1. Thedrum is partially filled with suitable liquid, such, for exam le. aswater, wh ch will flow through the orifice 33 until the l quid attainsan equal level in both compartments of the drum.

The liquid used in the drum will necessarily depend upon the nature ofthe fluid being metered. It is obvious that the liquid used to besatisfactory in the apparatus shown in Figs. 1-5 must be heavier than,and insoluble in the fluid being metered.

It will now be seen that as long as the fluid pressure in the twocompartments is equal, the drum will remain stationary,

through the orifice. from one in Fig. 4. Concern is divided into twosub- .ly thereof which serves to but in the event that the fluidpressure in either of the compartments becomes greater than in theother, liquid is forced compartment into the other and a rotation of thedrum will be caused by the greater weight of fluid on one side of theaxis of the drum.

It willbe further apparent that as such rotation takes place, due to theconstruction described above, the bores within the fittings I2 and,

I9 will remain in constant communication with the compartments withinthe drum, even though the drum may be rotated through a substantialnumber of degrees. Further, it will be clear that as rotation of thedrum takes place, the liquid in the drum may flow to the other throughthe orifice 33, thus maintaining the body of liquid within the drum insubstantially the same position at all times.

It will be apparent that the liquid used in the drum will depend uponthe fluid which is being metered. When a gas is being metered any liquidis satisfactory which will not dissolve an undue amount of the gas beingmetered. when a liquid is being metered a liquid must be used in thedrum which is heavier than and willenot mix with the liquid flowingthrough the main conduit.

' size as the instrument may be calibrated for any particular orifice.In place of an orifice the opening between the two compartments may takethe form of a nozzle or other type of opening through which the flow ofthe liquid takes place as a definite function of the difference of fromone compartment.

pressures existing in the two compartments. Figs. I

10, 11, and 12 show three forms of opening suitable for providingcommunication between the two compartments. In Fig. 10 an aperture inthe wall 30 is shown internally threaded to receive a casting 33 toprovide a. thin plate orifice. Fig. 11 a plate 33 is shown tion 30 andin Fig. 12 a casting 33 is shown threaded into an internally threadedaperture in the partition to provide communication between the chambersof a nature of the throat of a venturi. It will be apparent that in eachinstance these orifices may be easily removed and changed at will.

A reversing valve III is mounted upon the bracket 'I beneath the shelf2. This valve has a rotatable member mounted substantiallycentralcontrol the flow through the valve. A pair of conduits l2 and 43are connected to diametrically opposite sides of the valve, the conduit42 communicating with the bore I3 in the fitting I2-and the conduit 43connecting'with the bore 20 in the fitting I9. Also connected todiametrically opposite sides of the valve are a pair of conduits 44 andI5, which connect with the principal differential head device in theconduit through which the flow is tc be measured. 1'"

The connections to the princlpal'difi'erentia head device are not shownin Figs. 1 to 6, bu are clearly seen in the diagrammatic view of thlsecured to the partimodified form of the apparatus in Fig. '7. From theconstruction of the valve 4|] as seen in Fig. 6, it is apparent thatwhen the rotatable central portion of the valve is in the position' asshown in Fig. 6, the conduit 44 from the differential 'head device willbe in communication with the conduit 42, communicating with the fittingl2, the bore 9 in the shaft 1, and hence in direct communicationwith thecompartment 28 of the drum. Likewise, the conduit 45 from thediflerential head device will be in communication with the conduit 43and due to the connections described above, will be/in communicationwith the chamber 29 of the drum.

When the rotatable valve member 4| is moved through 90, it is apparentthat these connections will be reversed and the conduit 44 will then bein direct communication with chamber 28 of the drum and conduit 45 willthen communicate with chamber 28 of the drum. Due to the symmetricalconstruction of the rotatable valve member 4|, it will be seen that ifit is moved through a second 90' of rotation, it will again assumesubstantially the position shown in Fig. 6 and function as describedabove.

Automatic means are provided for'causing rotation of the reversing valve48. The rotatable member 4| of this valve extends laterally a shortdistance from the body of the valve and has rigidly secured thereto adisc 46 having an annular series of pins 41 spaced around the axis ofthe disc at 90 intervals. These pins extend through the disc andprotrude a short distance on either side thereof.

A solenoid 50 is secured to the under side of the web 2 which supportsthe shelf on which the drum is mounted. This solenoid is mounted in asuitable frame 5| and has depending therefrom a stirrup 52 which servesto limit downward movement of a reciprocable armature 53 slidablymounted within the solenoid.

The armature 53 has pivotally secured to its lower end 54 a slottedvalve actuating bar 55. The valve actuating bar 55 is slotted andmounted in such a' position that the disc 45 will extend into the slotthereof and has an extended lower end portion 51 extending a substantialdistance below the valve 48.

A second shelf 58 extends from the bracket l and has a slot thereinthrough which the lower end 51 of the bar 55 may pass. This slot, itwill be seen, serves to limit lateral movement of the bar 55. Each ofthe members of the bar 55 which lie on either side of the disc 45 isprovided with a tooth 80, adapted on its upper side to engage one of thepins 41 which pass through the disc 45. The lower side of the tooth 68is tapered gradually in order that it will engage the pins.

From the foregoing, it will be clear that when the solenoid 58 isenergized, the armature 53 will be drawn upwardly therein carrying withit the valve actuating bar 55 which is pivoted to the lower end thereof.As this valve actuating bar 55 is moved upwardly, the upper surface ofthe teeth 80 will each engage one of the pins 41 in the disc 48 and thusrotate the disc 48 through one-fourth of a revolution. When the solenoidis de-energized, the armature 53 will fall and the tapered lower surfaceof the tooth 68 will slide over the pin directly under the pin which ithas engaged on its previous upward movement and drop to a positiondirectly beneath this pin. Thus it is apparent that upon eachenergization of the solenoid, the disc 45 will be rotated. through 90.and, as has been described above,

such a rotation of the disc will cause a reversal of the connectionsbetween the differential head meter and the compartments in therotatable drum.

On the rear side of the drum on either side of the housing for theconduits 35 and 38 are mounted a pair of mercury switches 5 l. Each ofthese switches preferably comprises a closed capsule partially filledwith mercury and having a pair of contacts mounted in one end thereof.As is shown in Fig. 3, these switches are mounted on brackets in orderthat their angular position may be adjusted. It is apparent from theconstruction of the switches as shown that when the drum has beenrotated through a predetermined angular-distance, the-mercury will flowto the end of the capsule containing the contacts, closing, the circuitbetween the contacts and the switch.

These switches are each connected to a suitable source of electriccurrent and are in circuit with the solenoid 50, in order that, wheneither one of these switches are closed, the solenoid 58 will beenergized reversing the direction of flow of fluid through the valve 48.

As has been mentioned above, the conduits 44 and 45 are connectedadjacent the restricted orifice in a differential head meter in theconduit through which the flow is to be measured. When flow passesthrough this principal differential head meter, a pressure differentialwill be set up in the conduits 44 and 45. This pressure differentialwill, due to the construction of the reversing switch described above,be transmitted to the compartments 28 and 29 within the drum, and as hasbeen explained above, will cause a rotation of the drum and to thedifference in pressure existing on the surface of the liquid within thedrum. Continued existence of this pressure differential within the twochambers of the drum will cause the liquid within the drum to flowthrough the orifice 33 from one chamber into the other, causing arotation of the drumwhich will continue as long as any pressuredifferential exists in the two compartments, the speed of this rotationbeing substantially proportional to a definite function of the existingpressure differential. drum has been rotated through a predeterminedangular movement, the'mercury in one of the I switches 5| will close thecircuit through the solenoid 58 which will actuate the valve 46 toreverse the pressure differential existing in the compartments 2i and25.

' The reversal of this pressure differential will immediately cause arotation of the drum in the opposite direction until the other mercuryswitch 8! is closed and the operation repeated. It will be clearlyapparent from the foregoing that the.

speed of the rotation ofthe drum is dependent upon the magnitude of thepressure differential existing in the two compartments and also upon thesize of the orifice 33. a

In order to provide visual indication of the flow through the principaldifferential device a sta tionary indicating hand 88 is mounted upon oneof the bearings 5 extending upwardly adjacent in engagement with a pin12 extending through Further, it will be clear that after the 'gizationof the solenoid 50.

the lower portion of the bar 55, in order that the odometer may registerone unit upon each ener- It is clear from the foregoing that thesolenoid will be energized each time thedrum has been rotated through apredetermined angular distance, and it will be further clear thatenergization of the solenoid causes a reversal of a pressuredifferential withinthe drum and a reversal of the direction of rotationof the drum and consequently the odometer III will register the numberof times such reversal of the drum takes place.

In the diagrammatic views shown in Figs. '7 and 8, the structures shownand described in connection with the preceding figures have beensomewhat modified.

A cylindrical drum 15 similar in construction to the drum shown in thepreceding figures, is mounted for free rotation upon a stationary shaft16. The two compartments of this drum are connected by means of flexibleconduits H and 18 to the reversing valve 40. A pair of ears I9 protrudefrom the periphery of the drum and are spaced a On diametrically opposedsides of the drum aremounted a pair of stationary mechanical switches80, which comprise a pair of contacts extending into the path ofmovement of the ears IS. The switches 80 serve to control the circuitthrough the solenoid 50. It is apparent from this construction that aswas the case in the preceding construction, that after a predeterminednumber of degrees of angular movement of the drum, one of the switches80 will be closed, serving to actuate the reversing valve 40 to reversethe pressure differential existing within the two compartments of thedrum. A modified form of means for actuating the reversing switch isshown in Figs. 7 and 8. In this switch, a plate BI is rigidlyconnected'to the rotatable operating member of the switch and has atoothed periphery comprising four teeth spaced at 90 intervals. Theseteeth are engaged by a pin 82, carried in the bifurcated end of thesolenoid armature 83. The mounting and function of the odometer Hl shownin these figures is substantially the same as that described inconnection with the odometer shown in Figs. 1 to 6.

The differential head device 85 to which the conduits 44 and 45 areconnected is shown to be of the conventional Venturi type. However, itshould be borne in mind that the apparatus herein disclosed issusceptible of use with practically any form of differential head meterin which a pressure difierential is set up by means of flow through aconduit.

The function and operation of both modifications of the devices issubstantially the same.

The flow through the principal differential head device 85 creates afluid pressure differential in the conduits l4 and 45 and due to theconnection of these conduits to the rotary reversing valve'lO, thisdifference in pressure is transmitted directly to the two chamberswithin the rotatable drum. The action of this difference in pressure inthe two chambers on. the surface of the liquid contained in the drumcauses a rotation of the drum about its axis, due to' the flow of fluidthrough the spondingvariations in flow through the orifice 33 in thepartition in accordance with the pressure differential present in thecompartments of the drum, the rate of flow being substantiallyproportional to thesquare root of said pressure difference. Hence therate of rotation of the drum will be directly proportional to the rateof flow of fluid passing through the principal differential head device.w

After the drum has been rotated through a predetermined angularmovement, the circuit will be closed and the reversing switch actuatedto reverse the pressure differential and. rotate the drum in theopposite direction. By accurate con-- trol of the size of the orifice 33and the adjustment of the mercury switches 6|, it may be seen that acomplete cycle of operation of the apparatus may be adjusted torepresent a predetermined volume of fluid passing the principaldifferential head dethe drum may easily be converted to a definitesuitable angular distance apart less than 180 de- 'grees.

volumetric reading of the amount of fluid passing through the principaldifferential head device.

It will be understood that the movement of the.

following claims.

I claim:

1. A flow meter comprising means including a main conduit for thefluidwhose flow is to be measured and further including branch conduitswherein is produced a pressure difference which varies in proportion tothe square of the rate of flow of fluid in said main conduit, anoscillatable housing, means for connecting said branch conduits to saidhousing, pressure responsive means within said housing for causingmovement of said housing at a rate proportional to the square root ofthe pressure differential created in said conduits by the flow of fluidthrough said main conduit while preventing flow of said fluid throughthe housing and means for registering the oscillations of said housing.

2. In a flow meter, an oscillatable housing, conduits in communicationwith said housing, pressure responsive means within said housing wherebya pressure differential in said conduits will cause a movement of saidhousing at a rate at all times proportional to the square root of saidpressure differential and auxiliary power means independent of saidpressure differential and responsive to a predetermined movement of saidhousing for reversing said pressure differential in said conduits aftersaid housing has been moved through a predetermined angular distance.

3. In a flow meter for determining the volume of fluid passing through afluid main, a rotatable housing having a pair of chambers therein, apair of conduits providing communication between each of said chambersand points in said main whereby pressure differentials between saidpoints created by flow of fluid through said main will be transmitted tosaid chambers, pressure responsive means within said housing for causinga movement of said housing in accordance with the said pressuredifferential existing therein at a rate proportional to the square rootof such pressure differential, a valve for controlling the reversal ofsaid pressure differential and auxiliary power means independent of saidpressure differential for controlling said valve whereby said pressuredifferential maybe reversed to cause a reverse rotation of said housingafter a predetermined angular displacement of said housing, saidauxiliary power means being controlled by said predetermined angulardisplacement of said housing.

4. A flow meter comprising means to produce a pressure differenceresulting from the flow of fluid to be metered, two compartments, afluid in said compartments which is substantially nonmiscible with thefluid to be metered, means to apply the high pressure of the pressuredifference created in the flow of fluid to one compart-- ment and thelow pressure of the pressure difference to the other compartment, meansto alternate the compartments to which the high and low pressuredifferences are applied, connecting means between said compartmentsthrough which said non-miscible fluid passes from one compartment to theother at a rate proportional to the square root of said pressuredifference, said alternating means being set in operation by the passageof a predetermined quantity of the nonrniscible fluid through saidconnecting means and being independent of said pressure difference, thecontinued flow of fluid to be metered causing continued periodicaloperation of said alternating means and means to indicate the flow offluid to be metered.

5. A flow meter comprising means to produce a pressure differenceresulting from the flow of fluid to be metered, a verticallyoscillatable vessel, pivots therefor, said vessel having twocompartments, one on each side of said pivots, a'fluid in saidcompartments which is substantially nonmiscible with and having adifierent weight than the fluid to be metered, means to apply the highpressure of the pressure difference created in the flow of fluid to onecompartment and the low pressure of the pressure diflerence to the othercompartment, means to alternate the compartments to which the high andlow pressure differences are applied, connecting means between saidcompartments through which said non-miscible fluid passes from onecompartment to the. other at a rate proportional to the flow of fluid tobe metered, the flow of fluid to be metered changing the relativeamounts of the non-miscible fluid in said compartments and the changingrelative weights of the fluid in the compartments rocking said vessel onits pivots, said alternating means being set in operation by the rockingof said vessel a predetermined amount, the continued flow of the fluidto be metered causing continued periodical operation of said alternatingmeans and continued oscillation of said vessel.

6. A flow meter comprising avertically oscillate. blevessel, pivotstherefor, said vessel having. two compartments, one on each side of saidpivots, a body of sealing fluid in said compartments, means for applyingtwo different fluid pressures alternately to said compartments, meansactuated by the oscillations of said vessel to alternate the supply ofthe two different fluid pressures to said compartments, a connectionbetween said compartments through which the fluid in the com-- partmentspasses from one to the other at a rate proportional to the square rootof the diflerence in the two difierent fluid pressures, the passing ofsuccessive predetermined amounts of fluid from one compartment to theother oscillating said vessel on its pivots.

'7. A fluid meter comprising means to obtain a pressure differenceresulting from the flow of fluid being metered, said pressure differencebeing proportional to the square of the rate of such flow, two chamberswhose free volumes may be varied inversely to each other, means tosubject said chambers simultaneously to the high and low pressureeffects of said pressure difference to vary their respective freevolumes at a rate 8. A fluid meter comprising means to produce apressure difference as a function of the flow of fluid being metered,said pressure difference being proportional to the square of the rate ofsuch flow, two chambers, means to pass the high, then the low pressureof said pressure difference, alternately to each chamber at a rate ofalternation proportional to the square root of said pressure difference,and means responsive to said 'rate of alternation to indicate the volumeof the fluid flow.

9. A fluid meter comprising means to obtain a pressure differenceresulting from the flow of fluid being metered, said pressure differencebeing proportional to the square of the rate of such flow,

, two chambers, means to subject said chambers;

simultaneously to the high and low pressure effects of said pressuredifference alternately at a rate of alternation proportional to thesquare root of said pressure difference, means operable in response toeach-alternation, and 'means operable by said last mentioned means tocontinuously indicate the total volume of the fluid flow.

10. A flow meter comprising means including a main conduit for the fluidwhose flow is to be measured and further including branch conduitswherein is produced a pressure diiference which 'varies in proportion tothe square of the rate of flow of fluid in said main conduit, 2. housinghaving a dividing barrier located therewithin, means for connecting saidbranch conduits to said housing at opposite sides of said barrierwhereby the opposite sides of the latter are subjected to' pressures thedifierence of which is proportional to the pressure differenceaforementioned, means for causing movement of said barrier in oppositedirections relative to said housing alternately at a rate proportionalto the square root of the pressure difference resulting from thepressures to which the opposite sides thereof are'subjected, and meansfcr registering the alternate movements of said barrier.

11. A flow meter comprising means to produce a pressure differenceresulting from the flow of fluid to be metered, said pressure diflerencebeing proportional to the square of the rate of such flow, twocompartments, means to apply the high pressure of the pressuredifference created in the flow of fluid to one compartment and the lowpressure of the pressure difference to the other compartment, meansincluding an element associated with said compartments in a manner toprovide for relative, movement of the element at a rate proportional tothe square root of said pressure difl'erence, means to alternate thecompartmen-ts to which high and low pressures are applied after apredetermined relative movement of said element in one direction or theother, and means controlled by said last mentioned means to indicate thevolumetric flow of the fluid being metered.

12. A flow meter comprising means to obtain a pressure differenceresulting from the flow of fluid to be metered, said pressure differencebeing proportional to the square of the rate or such flow, two chambers,a movable barrier therebetween, means to apply simultaneously the highpressure of said pressure difference to one and the low pressure to theother of said chambers alterna-tely to cause relative movement of saidbarrier alternately in opposite directions whereby the free volumes ofsaid chambers are varied inversely relatively to each other, meansincluding a restriction associated with said chambers to insurevariation in said free volumes at a rate proportional to the square rootof said pressure difierence, and means for registering the number ofsuch alternate movements of such barrier, said number being utilized asa measure oi the total volumetric flow 01' the fluid.

' 13. In a flow meter for determining the volume of fluid passingthrough a fluid main, a housing having a pair of chambers therein, apair of conduits providing communication between each of said chambersand points in said main whereby pressure differentials between saidpoints created by flow of fluid throughsaid main will be transmitted tosaid chambers, a part associated with said chambers and relativelymovable with respect to another part in response to and at a rateproportional to the square root of the differential value of thepressures existing within said chambers, a valve for controllingthereversal of said pressure "differential with respect to saidchambers, and auxiliary independently operable power means responsive toa predetermined movement of said part first mentioned forcontrollingsaid valve to cause a reverse movement of said part first mentionedafter a given movement thereof in each direction.

14. A fluid meter comprising means to produce a pressure difierence as afunction of'the flow of fluid being metered, an auxiliary fluid, ahousing, an auxiliary restriction located in said housing and throughwhich said auxiliary fluid is adapted to flow, means to transmit anefiect of said pressure difference to said auxiliary fluid at oppositesides of said auxiliary restriction, means for reversing saidtransmitting means relative to said auxiliary restriction, and powermeans independent of the w of fluid being metered to actuate saidreversing means aiTa rate which is a function of the volume of auxiliaryfluid passing through the auxiliary restriction, the number ofoperations of said reversing means being utilized as a measure of thevolumetric flow of said fluid being metered.

' WILLIAM C. WALKER.-

